#' @param g1 [\code{\link{function}}]\cr
#'   The gradient of the first objective in \code{ind}. If missing, it will
#'   be approximated using \code{\link{estimateGradientBothDirections}}.
#' @param g2 [\code{\link{function}}]\cr
#'   The gradient of the second objective in \code{ind}. If missing, it will
#'   be approximated using \code{\link{estimateGradientBothDirections}}.
